Fly-by-Wire

So what is the best system right now that they are making the new planes with? what are the top of the line for airbus and boeing?

The A380-option is quite acceptabel: Power source are two independent hydraulic system for primary control, electrically driven actuators as back-up. Control via FBW with computer support of limited authority. That’s where both manufacturers go.

So what is the best system right now that they are making the new planes with? what are the top of the line for airbus and boeing?

I’m curious about the A380 systems? Got a link I can find out more. I understand each actuator has it’s own seperate motor/reservior much like the VC-10?

The A380 saves one hydraulic system (two instead of three) and uses these “electro-hydrostatic” actuators, which transfer electrical power via a small hydraulic pump (not sure). All critical flight controls have these actuators, but without hydraulics the controls become rather sluggish. So not very desirable.

thats not quite correct, some aircraft with conventional controls can still move the controls if all the hydraulics are lost, just that the load on the pedals/column is a lot higher. rather similar to you losing the power steering on your car.

Thank you for the info but the 727 uses a push-rod system right? and that was intact. the power comes from hydraulics on a 72 and when you have a failure of that system you looking at a problem so what are you trying to say?

Schorsch I didn’t say anything about the electrical system please explain.

I wanted to stress the two things you need to move a control actuator in a reasonable manner:

– CONTROL: either by a push-rod, wire or an electrical information system (FBW), digital or analog (or both at the same time).

– POWER: Usually by hydraulics or (some at A380) electro-hydrostyatic. Only for small aircraft and small airspeeds (Cessna) you don’t need an additional power-source.

Schorsch I didn’t say anything about the electrical system please explain.

I was flying a long time ago in a 727 and we had a hydraulic leak and had to make an emergency landing at JFK so if FBW uses hydraulic power to operate the control surfaces, would the pilots have any control if there was a leak or failure of some sort. the hydraulics on a 727 only control the landing gear but what if they control the control surfaces also.

The electrical system is just an mean to transport information. It doesn’t have anz power (to really understand the difference try to connect your toaster with your ethernet cable and put the power-plug in your LAN-plugin, you will recognize that the toast remains untoasted but fairly informed by internet while your computer blows up).
The only large civil aircraft which can fly with completly drained hydraulics is the A380. I don’t know about the B787, but that doesn’t fly at the moment so doesn’t count yet.

Yes, so just like a non-fbw aircraft a lot of redundancy is built in.

so what your saying is that a hydraulic failure is just as bad in FBW as in conventional controls. Right?

FBW aircraft use electrical signalling with hydraulic actuation whereas modern non-fbw aircraft just use hydraulics throughout. Flight control surfaces will be operated by at least 2 independent hydraulic systems and actuators for redundancy.

the 727 has hydraulics going to the flying controls as well as the undercarriage.
airliners have mulitple, independant hydraulic systems, so even if you have a leak in one, you can use another system to move the control.

I was flying a long time ago in a 727 and we had a hydraulic leak and had to make an emergency landing at JFK so if FBW uses hydraulic power to operate the control surfaces, would the pilots have any control if there was a leak or failure of some sort. the hydraulics on a 727 only control the landing gear but what if they control the control surfaces also.

… case the FBW systems weren’t faulty as you originally claimed!

Paul

Misunderstanding 🙂

The pilot got too low and the computer switched to a different mode. The pilot was definetly responsible, on the other hand I would not say he behaved irresponsible. He just didn’t know the system enough and wanted to perform a nice display. He actually unveiled the biggest issue on FBW computer aided and envelope protected aircraft: the pilot has to know, understand and use the offered systems right. Things that wiork in the heads of engineers and in the hands of test pilots don’t necessarily work in real life.

Absolutely corrrect and I agree completely, but this being the case the FBW systems weren’t faulty as you originally claimed!

Paul

most aircraft have back up systems to provide power to essential controls and systems. they provide electrical and hydraulic power by a variety of means.

Battery is sufficient for computers and will keep you online 30 minutes minimum. RAT [Ram Air Turbine] does it when all engines and APU breaks down. However, total loss of hydraulics and engines will give you no chance (only if you fly A-380) of control at all in lateral regime.

No, that wasn’t mentioned. The limiting factor of controls is often the availibility of hydraulic power. In some terms FBW has a disadvantage because it needs electricity while other flight controls directly pull on the actuator, therefore no need for electricity. Anyways, if hydraulic power is available so is electricity.

For military aircraft this may be of use because I have alternative ways. both convetional controls and FBW have already proven their reliability. The next step would be to take away the rudder panels from the pilot or to reduce his authority on it to a absolute minimum (yaw damper rules and pilot nmay give advice).

most aircraft have back up systems to provide power to essential controls and systems. they provide electrical and hydraulic power by a variety of means.

Has anyone yet mentioned that FBW systems offer a potentially greater degree of flight safety by allowing multiple, redundant control systems to co-exist ?

No, that wasn’t mentioned. The limiting factor of controls is often the availibility of hydraulic power. In some terms FBW has a disadvantage because it needs electricity while other flight controls directly pull on the actuator, therefore no need for electricity. Anyways, if hydraulic power is available so is electricity.

For military aircraft this may be of use because I have alternative ways. both convetional controls and FBW have already proven their reliability. The next step would be to take away the rudder panels from the pilot or to reduce his authority on it to a absolute minimum (yaw damper rules and pilot nmay give advice).

Has anyone yet mentioned that FBW systems offer a potentially greater degree of flight safety by allowing multiple, redundant control systems to co-exist ?

It’s never been proved the systems of the A320 that crashed at Habsheim was faulty. The aircraft should have performed the fly-past at 100 feet, not the 30 feet it was actually at, and so the computer did exactly what it was programmed to do..Land the plane. Pilot error was officially blamed.

Watching the video of the accident it’s amazing only 3 out of 136 people on board lost their lives.

Paul

The pilot got too low and the computer switched to a different mode. The pilot was definetly responsible, on the other hand I would not say he behaved irresponsible. He just didn’t know the system enough and wanted to perform a nice display. He actually unveiled the biggest issue on FBW computer aided and envelope protected aircraft: the pilot has to know, understand and use the offered systems right. Things that wiork in the heads of engineers and in the hands of test pilots don’t necessarily work in real life.